1. Field of Invention
This invention generally relates to detecting and maintaining good lateral image and paper registration in color image processing. More particularly, this invention relates to methods and systems in which image and paper registration adjustments are based on observing the movement of a photoreceptor belt.
2. Description of Related Art
Electrophotography, a method of copying or printing documents, is performed by exposing a light image representation of a desired document onto a substantially uniformly charged photoreceptor, such as a belt. In response to that light image, the photoreceptor discharges to create an electrostatic latent image of the desired document on the photoreceptor's surface. Developing material, or toner, is then deposited onto that latent image to form a developed image. That developed image is then transferred to a final substrate, such as paper. The surface of the photoreceptor is then cleaned of residual developing material and recharged in preparation for the production of another image.
Color images may be produced by repeating the above process once for each different colored toner that is used to make a composite color image. For example, in one color imaging process, referred to herein as the Recharge, Expose, and Develop, Image On Image (REaD IOI) process, a charged photoreceptor surface is exposed to a light image which represents a first color. The resulting electrostatic latent image is then developed with a first colored toner. The charge, expose and develop process is repeated for a second colored toner, then for a third colored toner, and finally for a fourth colored toner. The various differently colored toners are placed in superimposed registration on the first developed image so that a desired composite color image results. That composite color image is then transferred and fused onto an image recording substrate or medium.